The present invention is directed to a device driven by a motor receiving electric power, and repeatedly operated in the same load pattern. Hereinafter, such a device is called a “same load pattern device”.
According to a first configuration in which electric power is supplied to the motor from an inverter driven by an output of a battery-driven DC-DC converter, same load pattern devices assumed mainly include industrial devices such as a servo press, a die cushion for press, a transport device and a material handling device, but are not limited to them.
According to a second configuration in which the electric power is supplied to the motor from a wireless electric power transmission device, same load pattern devices assumed mainly include, but not limited to, industrial devices, such as a transport device mounted on a mobile device, e.g., an unmanned transport carriage, and a material handling device.
In the first configuration, the amount of loss in the above-described same load pattern device varies with parameters of a power conversion circuit such as an output voltage of a DC-DC converter, carrier wave frequency of an inverter or a voltage change ratio dv/dt of a switching waveform.
In the second configuration, the amount of loss in the above-described same load pattern device varies with parameters of the wireless electric power transmission device, such as oscillation frequency of the wireless electric power transmission device.
According to the first configuration, the “amount of loss” means the difference between electric power supplied from the battery and the motor output power, i.e., the amount of work lost as heat generation and electromagnetic radiation in the electric circuit (including the DC-DC converter, the inverter and the motor) from the battery to the motor and in the magnetic circuit inside the motor.
According to the second configuration, the “amount of loss” means the difference between electric power supplied from the wireless electric power transmission device and the motor output power, i.e., the amount of work lost as heat generation and electromagnetic radiation in the electric circuit from the wireless power electric transmission device to the motor and in the magnetic circuit inside the motor.
Regarding the first configuration, means for reducing this amount of loss have been already proposed in Patent Literature (PTL) 1, for example. The techniques relating to the present invention have been disclosed in PTL 2, Non-Patent Literature (NPL) 1 and NPL 2.
Regarding the second configuration, means for enhancing the transmission efficiency in a wireless electric power transmission device have already been proposed in, for example, PTLs 3 through 8.
PTL 1 discloses a technique of, when an operating condition of a device is changed, reducing the amount of loss by changing a parameter (carrier wave frequency of a DC-DC converter) of electric power conversion.
NPL 2 discloses a technique of reducing the loss by changing switching frequency during operation in accordance with a low-speed range, a medium-speed level and a high-speed range.